Sunday, January 19, 2014

This is today's update on the water leak from the MSIV (Main Steam Isolation Valve) Room of Reactor 3 at Fukushima I Nuclear Power Plant. (Previous posts on the subject are here and here.)

TEPCO says they did the nuclide analysis of the water sample that the robot collected. The temperature and the levels of contamination indicate it is the water that comes out of the Pressure Vessel/Containment Vessel.

TEPCO's way of saying it is that "the water is not the one that goes into the reactor."

However, the levels of contamination of this water is one to two orders of magnitude smaller than the highly contaminated water in the reactor building basements, which seems to me to indicate that this leaking water is diverted out of the Pressure Vessel it comes in full contact with the corium (wherever it is - part at the bottom of the PV, part buried into the concrete floor of the Containment Vessel).

The leaked water is higher in density of radioactive materials than the water being injected into the reactors. The temperature of the water is also higher. Therefore we believe this is not the leak of water that is being injected into the reactor. We will continue to investigate the cause of the leak.

TEPCO's alert has a link to the latest nuclide analysis of water samples taken at different stages of contaminated water treatment (published on 1/17/2014).

According to that analysis, the highly contaminated water that sits in the reactor building basement (supposedly after having come to full contact with the corium) has:

Cesium-134: 1.0×10^4 Bq/cm3 (10,000 Bq/cm3)

Cesium-137: 2.5×10^4 Bq/cm3 (25,000 Bq/cm3)

Cobalt-60: 1.4 Bq/cm3 (after treatment with SARRY)

All-beta: 2.3×10^4 Bq/cm3 (23,000 Bq/cm3, before RO treatment)

While the Japanese media continues to not see much significance of this leak, the workers who have been tweeting from Fukushima I NPP from the beginning of the accident seem to worry. The issue here is NOT whether this water is currently leaking into the surrounding environment. The issue is whether the MSIV and/or its ancillary systems failed in the March 2011 accident.

"Sunny" (from tweets here and here) fears the worst, that the MSIV itself is broken:

MSIV (Main Steam Isolation Valve) is a huge valve attached to the main steam pipe that connects the reactor building and the turbine building. When this valve closes, it means there is some extraordinary incident happening in the reactor core. Conversely, one might say that it would be a problem if this valve did not close in such an incident. Now, the water is leaking from there [from the MSIV]. In other words, the valve was not shut, or it broke.

The reactor core is scrummed, but the MSIV doesn't close or it breaks and [the coolant=water] leaks. Do you know how terrifying this is? Instead of talking about restarting [the nuclear power plants in Japan], we would need to stop all reactors in the world to deal with the problem, just like [when we stopped] PWRs after the Three Mile Island accident. Wait, what is more terrifying is, how many people are aware that this could be a serious problem?

Someone expressed his surprise to "Sunny" that TEPCO announced the incident at all, if this was such a serious incident. (People in Japan also love to say "TEPCO lies.") "Sunny"'s answer was:

この事象がそうなら世界中の全事業者とメーカーに情報共有するレベル

If this incident is what it is [the MSIV didn't close or broke in a severe emergency that necessitated the scrum], it should be shared with all nuclear plant operators and nuclear manufacturers in the entire world.

"Happy" hopes it is not the MSIV itself but ancillary pipe(s) that broke:

In the MSIV Room, other than the Main Steam Isolation Valve there are other systems and many small pipes, many of which connects directly to the reactor. We need to closely investigate inside the room to find out the cause [of the leak], but I'm afraid it will be a rather difficult task. The radiation level is high for workers to work inside, and it would be difficult for robots to navigate because of numerous pieces of equipment and pipes in a narrow space.

So was it a LOCA (Loss of Coolant Accident) because of either the failure of the MSIV or the ancillary system that is not supposed to fail, in addition to the water boiling off by the decay heat?

But as Happy says, the radiation levels are particularly high near the area of the leak (amounting to Sieverts/hour), and how TEPCO is going to "further investigate", as reported by happy-go-lucky media like NHK, is unknown.

9
comments:

Anonymous
said...

If TEPCO believes its own press releases, in their minds, they have an explanation and are not to worried about the situation. Hopefully they are not to busy to consider it.

If a detonation took place, I doubt the behemoth isolation valve was design to withstand such a shock wave. If the valve was damage after the meltdown was in full swing, I don't know how it makes any difference now if it failed or not.

None of the primary containments hold water except at basement levels which could be groundwater level for all we know. The isolation valve could be perfectly good but the primary containment shell can't hold water until you get to the suppression doughnut level, inside or out in the basement. So what's the point?

The undersized Mark I containment is a well known design flaw but they were built anyway and this is the result...a flawed design in practice.

Anon at 10:07PM, about TEPCO's way of saying things, remember that to them (and NISA), a basement flooded with contaminated water was a "water puddle", and hydrogen explosions that blew off the top floors of Reactors 1 and 3 were "loud noise" and "white smoke".

At those cesium levels in the basement water the levels in the MSIV leak water may be dilution of the basement water, literally. Wherever water is being continually added, RPV or CV, makes its way to the basement and from the basement is eventually lost.

There's probably residue of fuel rods, too, in the CV and RPV, that didn't drop to the basement.

Didn't Tepco do a borascope examination of the pressure vessel a long time ago and discover that there was no water in it? If so, the water leak cannot be coming from the pressure vessel unless Tepco has discovered a way of making water flow uphill.

20 degrees C is about the same temperature as the bottom of the pressure vessel.

Endoscope prove of the CV that TEPCO did was for Reactor 1 and Reactor 2. Reactor 3's radiation levels are too high for the operation done in a similar manner (i.e. sending in human workers), though TEPCO seems to be planning to do it with the help of robots. I don't think it's done yet.

About my coverage of Japan Earthquake of March 11

I am Japanese, and I not only read Japanese news sources for information on earthquake and the Fukushima Nuke Plant but also watch press conferences via the Internet when I can and summarize my findings, adding my observations.

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